1. Field of the Invention
The present invention relates to a liquid crystal display device that can reliably mount a printed circuit board.
2. Description of Related Art
A liquid crystal display device is a thin, lightweight device with low power consumption, which is widely used for a notebook PC, a PC monitor, a home television set, and the other appliances. In the liquid crystal display device, lights emitted from a back light transmit a liquid crystal panel to form video.
The liquid crystal display device has a plurality of printed wiring boards arranged thereon, and the individual printed wiring boards have electronic components mounted thereon. The liquid crystal display device is formed in such a way that printed wiring boards are arranged on the back surface of a rear frame formed of a bent metal plate, and on the back surface of the rear frame, a plurality of support base parts is formed so as to elevate by extruding. The printed wiring boards are bolted to a plurality of support base parts.
FIG. 10 shows a perspective view seen from the back surface side of a conventional liquid crystal display device, and FIG. 11 shows a side view depicting a support base part of a rear frame of the conventional liquid crystal display device. As shown in FIG. 10, the liquid crystal display device before has a support base part 93 that projects from the under surface of a bottom part 11 of a rear frame 1, and a printed wiring board 61 is fixed with a bolt Bt through the support base part 93 (see FIG. 11). As shown in FIG. 11, the support base part 93 has a pair of support leg parts 931 that stand from the back surface of the bottom part 11, a rectangular base part 932 to both ends part of which a pair of the support leg parts 931 is joined, and an internal thread hole 933 that is formed in the base part 932.
In the support base part 93, the support leg parts 931 obliquely stand so as to come close to each other from the bottom part 11. The rear frame 1 is formed in one piece with the support leg part 931, and the support leg part 931 is formed in one piece with the base part 932. A connecting part 934 of the rear frame 1 to the support leg part 931 and a connecting part 935 of the support leg part 931 to the base part 932 are formed of curved surfaces having a small curvature radius.
As shown in FIG. 11, when the printed wiring board 61 is arranged on the support base part 93, the support leg parts 931 are arranged closely to the mounting part of the printed wiring board 61 on the support base part 93. Near the mounting part on the support base part 93, a prohibiting area Pf is formed on which no electronic components are mounted in order to prevent the terminals of the electronic components from being contacted with the support leg parts 931. The wiring pattern of the printed wiring board 61 is designed such a way that no electronic components are mounted on the prohibiting area Pf.
In addition, such a scheme is proposed that a truncated conic support base part is used to fix a printed wiring board (see Japanese utility Model Registration No. 3108915, JP-A-2003-167231, and JP-A-2006-227057). Also in this case of the truncated conic support base part, a prohibiting area is similarly formed near the mounting part of the truncated conic support base part and the wiring pattern of the printed wiring board is formed so as not to mount electronic components on the prohibiting area.
When a printed wiring board is upsized, the printed wiring board is sometimes warped or bent due to its weight. In order to suppress this warpage or bend, it is necessary to increase a support part supported by a support base part, which correspondingly expands a prohibiting area. On this account, the wiring pattern has to be laid out except the prohibiting area, and the sizes of the wiring pattern itself and the printed wiring board itself are increased.
When the sizes of the layout of the wiring pattern and the printed wiring board are increased, a large number of materials are necessary to form the wiring pattern and the printed wiring board. When the size of the wiring pattern is reduced as the prohibiting area is left, the printed wiring board itself is downsized but the flexibility of the layout of the wiring pattern is dropped, or the layout has a smaller margin, which might cause operational defects due to noise or short circuits.